crank seals or not???

[souphmars]

what r some way ways u can determine that the crank seals r bad without taking anything major apart????i have done all the jetting and cleaning u can do to a carb???i am thinking it is the crank seals or something in the ignition...it is a 1998 yz250-thanx for all the info

[Woodsie]

Easist thing to do is take left sidecover off (flywheel side), start bike, spray starting fluid, or wave an unlit propane torch, (valve open) over all critical leak areas (carb boot, behind flywheel, head, etc.) AVOID SPRAYING SPARK PLUG !!!! FLAMES!!!!

Watch for any rise in RPMs


Best thing to do is a leakdown test. Try to find someone who has the test kit. I made fixtures myself, to plug off carb and exhaust.
If you need procedure, let me know.

[KTM250rm393]

A way to test to see if the crankseal on the tranny side is bad is to use either ATF tranny fluid type 'F' or get you a bottle of Bel Ray Gearseaver 80 wt and put it in your tranny. If she smokes white smoke like a steam locomotive, you got bad crank seals.

White smoke crank seals bad (only when using a hydraulic base oil), blue smoke is jetting issue.

[souphmars]

i used 20-50 castrol for tranny oil-i will try a type f-to see if it will have white smoke-i will also try spraying-i sprayed with wd-40 and didn't get a surge-i will try starting fluid

[KTM250rm393]

souphmars,

Regular engine oil won't smoke bad if its getting into the engine from the crank seals. It will only foul your plug. Its hard to tell from regular blue smoke from 2 stroke oil.

On the other hand, tranny fluid will smoke WHITE when it burns. Its worse than the worst fog you've ever been in.

Use the tranny fluid and ride around for like 10 mins and see if you get an all white smoke coming from your exhaust. Another thing is to measure out your oil, pour it in. Ride it for 20-30 mins and drain the tranny and see if you drain out approx. what you put into it.